This invention relates to a novel and economical process to break down particles of cellulose-containing plants into smaller polymers and compounds which are highly reactive chemically and are soluble in water and/or common organic solvents.
The process in this invention differs from the process commonly known in the arts to produce alkali metal cellulose by heating the cellulose in a concentrated aqueous solution of the alkali metal hydroxide to break down the cellulose polymers; the alkali metal cellulose produced is not soluble in water and must be reacted with carbon disulfide before it is water soluble. In the process of this invention, aqueous solutions are not used and a much higher temperature is necessary to break down the cellulose polymers in plants in order for it to be water soluble. It is not necessary to remove the lignin for wood in the process of this invention. When an organic or inorganic acid is added to the broken-down alkali metal cellulose polymer, carbon dioxide is given off. The dark brown alkali metal cellulose polymer is usually converted to a cream color after the cellulose is reacted with other organic reactants, especially in an acetic medium.
When wood is used as the cellulose-containing plant, the usual lignin-cellulose bond is not broken in most of the cases, but the molecules of cellulose are broken down into smaller molecules which are water soluble and highly reactive chemically, especially with aldehydes, furan compounds, polyisocyanate compounds and polyurethane prepolymers.
The broken-down polymers of cellulose-containing plants are commercially useful polymers. The alkali cellulose of cellulose-containing plants is highly reactive. It will produce useful resins by reacting with aldehydes, ketones, isocyanates, vinyl acetate acrylic acid monomers, polyfunctional alkylating agents, monofunctional alkylating agents, aldehydes and phenols, aldehydes and amino compounds, vinyl acetate with other vinyl monomers, acrylic acid compounds with other vinyl monomers, epihalohydrins with polyamines, oxidated silicon compounds, sulfur, silicon halides, organic polyhalides and polyamines, furfuryl alcohol, compounds which contain halogen atoms capable of being quaternized or R--SO.sub.2 --groups, epoxide compounds and mixtures thereof.
The aqueous solution of the alkali metal cellulose polymers of cellulose-containing plants may be used commercially to react with polyisocyanate and isocyanate-terminated polyurethane prepolymers and isocyanate-terminated polyurethane silicate prepolymers. They may be polymerized with organic aldehydes, furfuryl alcohol, epihalohydrins and polyamine organic polyhalide compounds, organic epichlorohydrin compounds and a polyamine halohydrins, ketones, organic epoxides, acrylic compounds, vinyl acetate, organic halides, organic polyhalides, organic acid sulfates, organic poly(acid sulfates), organic nitrates, organic polynitrates, organic acid phosphates, organic poly(acid phosphates), organic bicarbonate, organic poly(bicarbonate) compounds containing radicals, organic compounds containing formate radicals, organic compounds containing poly(formate) radicals, organic compounds containing acetate, propionate, laurate, oleate, stearate, oxalate, acid malonate, acid tartrate, acid citrate radical and mixtures thereof.
The water-soluble broken-down alkali metal cellulose polymer may be precipitated by the addition of a salt-forming compound, such as an organic or inorganic acid. The water is filtered off. The water contains 5% to 30% by weight of plant polymers and, in the case of wood, some lignin is present. The degraded cellulose polymers are precipitated as dark brown to black fine particles which are soluble in acetic acid, alcohols, dilute alkali hydroxide solutions and other organic solvents. The broken-down cellulose polymers may be chemically reacted with isocyanate compounds, polyisocyanate compounds, polythioisocyanate compounds, silicon halides, polycarboxyl acids and their corresponding anhydride, epoxides, aldehydes, ketones, furfuryl alcohol, epihalohydrins and mixtures thereof.
The water-soluble broken-down cellulose polymers and lignin are soluble in acetic and basic aqueous solutions. They may be used in the aqueous solution to produce resins by reacting with furfural, furfuryl alcohol, aldehyde and an amino compound, aldehyde and a phenol compound, aldehydes, ketones, epoxides and polyamines, polyhalide organic compounds and polyamines, isocyanates and mixtures thereof. The salt may be removed by washing the resins with water and filtering. The water-soluble broken-down cellulose polymers may be recovered by evaporating the water, then extracting the polymers from the salt by using an organic solvent, and then evaporating the organic solvent. The tan-colored cellulose polymer may be used in the production of polyurethane resins and foams, phenoplast, aminoplasts, aldehyde cellulose resins, ketone cellulose resins, furfuryl alcohol-cellulose resins, cellulose silicone polymers and as a filler in paints, varnishes, organic resins, etc.
When desirable, a higher percentage of alkali metal cellulose polymers may be produced, which are not water soluble, be regulating the temperature and the length of time the alkali metal hydroxide and cellulose-containing plants are heated. These polymers are highly reactive, as previously discussed.
Any suitable cellulose-containing plant or the products of cellulose-containing plants which contain cellulose may be used in this invention. The plant material is preferred to be in the form of small particles such as sawdust. In nature, cellulose is widely distributed. It is found in all plants and they may be used in this process, preferably in a dry, small-particle form.
Suitable cellulose-containing plants include, but are not limited to, trees, e.g., spruce, pine, hemlock, fir, oak, ash, larch, birch, aspen, poplar, cedar, beech, maple, walnut, cypress, redwood, cherry, elm, chestnut, hickory, locust, sycamore, tulip, tupelo, butternut, apple, alder, magnolia, dogwood, catalpa, boxwood, crabwood, mahogany, greenheart, lancewood, letterwood, mora, prima vera, purpleheart, rosewood, teak, satinwood, mangrove, wattle, orange, lemon, logwood, fustic, osage orange, sappanwood, Brazilwood, barwood, camwood, sandalwood, rubber, gutta, mesquite, and shrubs, e.g., oleander, cypress, junipers, acanthus, pyracantha, ligustrum, lantana, bougainvillea, azalea, feijoa, ilex, fuscia, hibiscus, datura, holly, hydrangea, jasmine, eucalyptus, cottoneaster, xylosma, rhododendron, castor bean, eugenia, euonymus, fatshedera, aralia, etc., and agricultural plants, e.g., cotton, cotton stalks, corn stalks, corn cobs, wheat straw, oat straw, rice straw, cane sugar (bagasse), soybean stalks, peanut plants, pea vines, sugar beet waste, sorghum stalks, tobacco stalks, maize stalks, barley straw, buckwheat straw, quinoa stalks, cassava, potato plants, legume vines and stalks, vegetable inedible portion, etc., weeds, grasses, vines, kelp, flowers and algae. Wood fibers and cotton fibers are the preferred cellulose-containing materials. The waste products of agricultural plants which contain cellulose may be air-dried, then ground into small particles and used in this invention. Commercial waste products containing cellulose, e.g., paper, cotton cloths, bagasse wallboard, wood products, etc., may be used in this invention. Wood with the lignin removed (wood pulp) may be used in this invention.
Cellulose-containing plants which have been partially decomposed, such as humus, peat and certain soft brown coal, may be used in this invention.
Other products of cellulose-containing plants may be recovered in the process of this invention such as waxes, gums, oils, sugars, wood alcohol, agar, rosin, turpentine, resins, rubber latex, dyes, etc.
Any suitable aldehyde may be used in this invention, such as formaldehyde, acetaldehyde, butyl aldehyde, chloral, acrolein, furfural, benzaldehyde, crotonaldehyde, propionaldehyde, pentanals, hexanals, heptanals, octanals and their simple substitution products, semi-acetals and full acetals, paraformaldehyde and mixtures thereof. Compounds containing active aldehyde groups such as hexamethylene tetramine may also be used.
Any suitable amino compound may be used in this invention such as urea, thiourea, alkyl-substituted thiourea, alkyl-substituted ureas, melamine, aniline, quanidine, saccharin, dicyandiamide, benzene sulfonamides, toluene sulfonamide, aliphatic and aromatic polyamines and mixtures thereof. Urea is the preferred amino compound, and formaldehyde is the preferred aldehyde when used with an amino compound.
Any suitable phenol compound may be used in this invention such as phenol, p-cresol, o-cresol, m-cresol, cresylic acid, xylenols, resorcinol, cashew nut shell liquids, anacordol, p-tert-butyl phenol, Bisphenol A, creosote oil, 2,6-dimethylphenol and mixtures thereof. Phenol is the preferred phenol compound and formaldehyde is the preferred aldehyde when used with a phenol compound.
Any suitable mixture of the amino compounds and phenol compounds with an aldehyde may be used in this invention.
Any suitable acid compound, inorganic or organic, may be used for salt formation, including those which also have a chainbuilding function such as sulphurous acid, sulphuric acid, hypophosphorous acid, phosphinic acids, phosphonous acids and phosphonic acid, glycolic acid, lactic acid, succinic acid, tartaric acid, oxalic acid, phthalic acid, trimellitic acid and the like. Further examples of acids may be found in German Pat. No. 1,178,586 and in U.S. Pat. No. 3,480,592. Acids such as hydrochloric, fluoroboric acid, amidosulphonic acid, phosphoric acid and its derivatives, acetic acid, propionic acid, etc., may be used. Inorganic hydrogen-containing salts may be used such as sodium hydrogen sulphate, potassium hydrogen sulphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate and mixtures thereof.
The acid compounds may be used to react with the alkali metal atoms in the alkali metal cellulose polymer to produce a salt and also release CO.sub.2 which expands the cellulose polymer into a cellular solid product. The acid compounds may also be used as a catalyst in the reactions to produce foamed aminoplast-cellulose products, foamed phenoplast-cellulose products and aminoplast-cellulose-phenoplast foamed products. These acid compounds may also be used in the production of polyurethane-cellulose cellular solid products to react with the alkali metal atoms to form a salt. The acid compounds may be used to precipitate the alkali metal cellulose from an aqueous solution.
Any suitable oxidated silicon compound may be used in this invention such as silica, e.g., hydrated silica, silicoformic acid, silica sol, etc., alkali metal silicates, alkaline earth metal silicates, natural silicates with free silicic acid groups and mixtures thereof. The hydrated silica includes various silicon acids such as silicic acid gel, orthosilicic acid, metasilicic acid, monosilandiol, polysilicoformic acid, etc. Hydrated silica is the preferred oxidated silicon compound.
Any suitable organic polyisocyanate may be used according to the invention, including aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates. Suitable polyisocyanates are, for example, arylene polyisocyanates such as tolylene, metaphenylene; 4-chlorophenylene-1,3-; methylene-bis-(phenylene-4-); biphenylene-4,4'-; 3,3-dimethoxy-biphenylene-4,4'-; 3,3'-diphenylbiphenylene-4,4'-; naphthalene-1,5- and tetrahydronaphthalene-1,5-diisocyanates and triphenylmethane triisocyanate; alkylene polyisocyanates such as ethylene, ethylidene; propylene-1,2-; butylene-1,4-; butylene-1,3-; hexylene-1,6-; decamethylene-1,10-; cyclohexylene-1,2-; cyclohexylene-1,4-; and methylene-bis-(cyclohexyl-4,4'-) diisocyanates.
It is generally preferred to use commercially readily available polyisocyanates, e.g., tolylene-2,4- and -2,6-diisocyanate and any mixtures of these isomers, ("TDI"), polyphenylpolymethylene-isocyanates obtained by aniline-formaldehyde condensation followed by phosgenation ("crude MDI"), and polyisocyanates which contain carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups, imide groups or biuret groups, ("modified polyisocyanates"). Inorganic polyisocyanates are also suitable according to the invention. Suitable polyisocyanates which may be used according to the invention are described, e.g., by W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136.
Solutions of distillation residues accumulating during the production of tolylene diisocyanate, diphenyl methane diisocyanate or hexamethylene diisocyanate, in monomeric polyisocyanates or in organic solvents and mixtures thereof may be used in this process. Phosgenation products of condensates of aniline or anilines alkylsubstituted on the nucleus, with aldehydes or ketones, may be used in this invention.
Organic polyhydroxyl compounds (polyols) may be used in this invention with polyisocyanates or may be first reacted with a polyisocyanate to produce isocyanate-terminated polyurethane prepolymers and then also used in this invention.
Reaction products of from 50 to 99 mols of aromatic diisocyanates with from 1 to 50 mols of conventional organic compounds with a molecular weight of, generally, from about 400 to about 10,000, which contain at least two hydrogen atoms capable of reacting with isocyanates, may also be used. While compounds which contain amino groups, thiol groups or carboxyl groups may be used, it is preferred to use organic polyhydroxyl compounds, in particular, compounds which contain from 2 to 8 hydroxyl groups, especially those with a molecular weight of from about 800 to about 10,000 and preferably from about 1,000 to about 6,000, e.g., polyesters, polyethers, polythioethers, polyacetals, polycarbonates or polyester amides containing at least 2, generally from 2 to 8, but preferably from 2 to 4, hydroxyl groups, of the kind known for producing homogeneous and cellular polyurethanes.
The hydroxyl group containing polyesters may be, for example, reaction products of polyhydric alcohols, preferably dihydric alcohols, with the optional addition of trihydric alcohols, and polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or their mixtures may be used for preparing the polyesters. The polycarboxylic acid may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may be substituted, e.g., with halogen atoms and may be unsaturated. Examples include: succinic acid, adipic acid, sebacic acid, suberic acid, azelaic acid, phthalic acid, phthalic acid anhydride, isophthalic acid, tetrahydrophthalic acid anhydride, trimellitic acid, hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride, fumaric acid, maleic acid, maleic acid anhydride, dimeric and trimeric fatty acids such as oleic acid, optionally mixed with monomeric fatty acids, dimethylterephthalate and bis-glycol terephthalate. Any suitable polyhydric alcohol may be used such as, for example, ethylene glycol; propylene-1,2- and -1,3-glycol; butylene-1,4- and -2,3-glycol; hexane-1,6-diol; octane-1,8-diol; neopentyl glycol; cyclohexanedimethanol-(1,4-bis-hydroxymethylcyclohexane); 2-methyl-propane-1,3-diol; glycerol; trimethylol propane; hexane-1,2,6-triol; butane-1,2,4-triol; trimethylol ethane; pentaerythritol; quinitol; mannitol and sorbitol; methylglycoside; diethylene glycol; triethylene glycol; tetraethylene glycol; polyethylene glycols; dipropylene glycol; polypropylene glycols; dibutylene glycol and polybutylene glycols. The polyesters may also contain a proportion of carboxyl end groups. Polyesters of lactones, such as .epsilon.-caprolactone, or hydroxycarboxylic acids such as .omega.-hydroxycaproic acid, may also be used.
The polyethers with at least 2, generally from 2 to 8 and preferably 2 or 3, hydroxyl groups used according to the invention are known and may be prepared, e.g., by the polymerization of epoxides, e.g., ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin, each with itself, e.g., in the presence of BF.sub.3, or by addition of these epoxides, optionally as mixtures or successively, to starting components which contain reactive hydrogen atoms such as alcohols or amines, e.g., water, ethylene glycol; propylene-1,3 or 1-2-glycol; trimethylolpropane; 4,4-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine or ethylenediamine. Sucrose polyesters such as those described, e.g., in German Auslegeschriften Nos. 1,176,358 and 1,064,938, may also be used according to the invention. It is frequently preferred to use polyethers which contain predominantly primary OH groups, (up to 90% by weight, based on the total OH groups contained in the polyether). Polyethers modified with vinyl polymers such as those which may be obtained by polymerizing styrene or acrylonitrile in the presence of polyethers, (U.S. Pat. Nos. 3,383,351; 3,304,273; 3,523,093 and 3,110,695; and German Patent No. 1,152,536) and polybutadienes which contain OH groups are also suitable.
By "polythioethers" are meant, in particular, the condensation products of thiodiglycol with itself and/or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols. The products obtained are polythio-mixed ethers or polythioether ester amides, depending on the cocomponent.
The polyacetals used may be, for example, the compounds which may be obtained from glycols, e.g., diethylene glycol, triethylene glycol, 4,4'-dihydroxydiphenylmethylmethane, hexanediol, and formaldehyde. Polyacetals suitable for the invention may also be prepared by the polymerization of cyclic acetals.
The polycarbonates with hydroxyl groups used may be of the kind, e.g., which may be prepared by reacting diols, e.g., propane-1,3-diol; butane-1,4-diol; and/or hexane-1,6-diol or diethylene glycol; triethylene glycol or tetraethylene glycol, with diarylcarbonates, e.g., diphenylcarbonates or phosgene.
The polyester amides and polyamides include, e.g., the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, diamines, polyamines and mixtures thereof.
Polyhydroxyl compounds which already contain urethane or urea groups, modified or unmodified natural polyols, e.g., castor oil, carbohydrates and starches, may also be used. Additional products of alkylene oxides with phenolformaldehyde resins or with urea-formaldehyde resins are also suitable for the purpose of the invention.
Examples of these compounds which are to be used according to the invention have been described, e.g., in High Polymers, Volume XVI, "Polyurethanes, Chemistry and Technology", published by Saunders-Frisch Interscience Publishers, New York, London, Volume I, 1962, pages 32 to 42 and pages 44 to 54 and Volume II, 1964, pages 5 to 6 and 198 to 199; and in Kunstsoff-Handbuch, Volume VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Munich, 1966, e.g., on pages 45 to 71.
If the polyisocyanates or the prepolymer which contains NCO groups have a viscosity above 2000 cP at 25.degree. C., it may be advantageous to reduce the viscosity thereof by mixing it with a low-viscosity organic polyisocyanate and/or an inert blowing agent or solvent.
Inorganic polyisocyanates and isocyanate-terminated polyurethane silicate prepolymers may also be used in this invention.
When an aqueous solution of alkali metal cellulose polymer is being used to react with, or as a curing agent for, polyisocyanates, it is advantageous in certain cases to use catalysts such as tertiary amines, e.g., triethylamine, tributylamine, N-methyl-morpholine, N-ethyl-morpholine, tetramethylthylenediamine, pentamethyldiethylenetriamine, triethanolamine, triisopropanolamine, organo-metallic compound, e.g., tin acetate, tin octoate, tin ethyl hexoate, dibutyl tin diacetate, dibutyl tin dilaurate and mixtures thereof.
Other examples of catalysts which may be used according to the invention and details of their action are described in Kunstsoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich, 1966, e.g., on pages 96 and 102. Silaamines are suitable catalysts, e.g., 2,2,4-trimethyl-2-silamorpholine or 1,3-diethyl aminomethyl tetramethyl disiloxane. Suitable catalysts are also tetraalkyl ammonium hydroxides, alkali phenolates, alkali metal hydroxides, alkali phenolates, alkalialcoholates and hexahydrotriazines.
Suitable flame-resistant compounds may be used which contain halogen or phosphorus, e.g., tributylphosphate; tris(2,3-dichloropropyl)-phosphate; polyoxypropylenechloromethylphosphonate; cresyldiphenylphosphate; tricresylphosphate; tris-(bets-chloroethyl)-phosphate; tris-(2,3-dichloropropyl)-phosphate; triphenylphosphate; ammonium phosphate; perchlorinated diphenyl; perchlorinated terephenyl; hexabromocyclodecane; tribromophenol; dibromopropylidiene; hexabromobenzene; octabromodiphenylether; pentabromotoluol; poly-tribromostyrol; tris-(bromocresyl)-phosphate; tetrabromobis-phenol A: tetrabromophthalic acid anhydride; octabromodiphenyl; tri-(dibromopropyl)-phosphate; calcium hydrogen phosphate; sodium or potassium dihydrogen phosphate; disodium or dipotassium hydrogen phosphate; ammonium chloride; phosphoric acid; polyvinylchloride tetomers chloroparaffins as well as further phosphorus- and/or halogen-containing flame-resistant compounds as they are described, e.g., in "Kunststoff-Handbuch", Volume VII, Munich 1966, pages 110-111, which is incorporated herein by reference. The organic halogen-containing components are, however, preferred in the polyurethane-cellulose and polyurethane-cellulose-silicate cellular solid products. In the production of aldehyde cellulose, amino-aldehyde-cellulose and phenolaldehyde-cellulose cellular solid product, phosphoric acid may be used to react with the alkali metal atoms, thereby producing an alkali metal hydrogen phosphate which may be used as the flame-resistant compound.